Below, nestled amongst my collection of elephants and cowboys, can be seen my collection of Galilean thermoscopes. Everybody gotta collect sumptin'.
Explanations of how these thermometers function can be found on line. I have read several articles that describe the process very clearly, but I still don't understand it. I especially don't understand how mine work as each of them registers a different temperature, a disparity that can be explained in various ways: Galileo was wrong, there are extraordinarily local variations in the temperature of my living room or I was sold a load of old tat.